4. ESTUDIO COMPARATIVO
4.1. EVOLUCIÓN DE LA MARCA BLANCA
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SYSTEM OF AMENDMENTS AND REVISION
I N T E N T I O N A L L Y L E F T B L A N K
TABLE OF CONTENTS
TABLE OF CONTENTS
1.5 AUSTRALIA PACIFIC . . . 25
1.5.1 South East Asia and North West Australia. . . 25 1.5.2 Australia . . . 25 1.5.3 Stream Weather . . . 26 1.5.4 Airmasses . . . 27 1.5.5 Tropical Cyclones. . . 29 1.5.6 The Tropopause . . . 29 1.5.7 Upper Winds . . . 29 1.5.8 Aerodromes in the Region . . . 301.6 AFRICA . . . 39
1.6.1 Major Influences. . . 39 1.6.2 Winter. . . 40 1.6.3 Jetstreams and Upper Winds. . . 40 1.6.4 Tropical Revolving Storms . . . 40 1.6.5 Aerodromes in the Region . . . 41WEST ASIA AND MIDDLE EAST WEATHER
1. METEOROLOGY
1.1. WEST ASIA AND MIDDLE EAST WEATHER
1.1.1. Winter and Spring (November to April)Cold fronts from West produce cumulonimbus and squall lines over the eastern Mediterra-nean sectors occasionally reaching as far as Tehran. The Tehran area is also affected by cold fronts from the North which produce widespread stratus, fog, drizzle and snow.
Warm fronts may affect the routes near and to Tehran. They move from Southeast to North-west and the warm air comes from the Gulf Area. They produce overcast weather with rain, drizzle and occasionally snow. East of Tehran and the Gulf Area frontal passages are rare. If they do occur, they produce layers of stratocumulus and cumulus with scattered thunder-storms. In the Gulf, fog occurs during this period, but formation is rare before 2:00 A.M., the worst month being February. Rainfall is in the form of showers or occasional cumulonimbus, normally of short duration.
Problems with dust haze are negligible, except with occasional squally winds associated with cumulonimbus.
1.1.1.1. Jetstreams and Upper Winds
Jetstreams will be found over the whole area. The main direction is from the west or occa-sionally southwest. Wind forecasts may be wrong due to the movement of the jet stream areas. Average strength 60-90 knots with the maximum 120-150 knots.
1.1.1.2. Turbulence
Clear Air Turbulence in connection with the jetstreams. Mountain wave turbulence may occur over Beirut/Ankara, Tehran and Karachi
1.1.1.3. Thunderstorms
There can be very severe cumulonimbus activity at the change over from winter to summer in March and from summer to winter in the autumn, with violent thunderstorms and associated up and down drafts and down bursts. Isolated thunderstorms may occur, especially in May, they usually have a base of around 6000 feet moving slowly to the Northeast.
1.1.1.4. Dust and Sand Storms
Found in the desert region of Egypt, Sudan, Iraq, Iran, the Gulf area and Pakistan. Often associated with gusty thunderstorms or frontal windshifts, when the surface winds are greater than 20-25 knots. In these storms the air is ruled with dust/sand particles up to at least 15000 feet. These occur at any time of the year most frequently during spring, summer and autumn.
WEST ASIA AND MIDDLE EAST WEATHER
1.1.2. Summer and Autumn (May to October)
Frontal activity over the majority of the routes is generally absent except for weak systems affecting Istanbul/Ankara. Good flying weather with mostly clear sky. In the Gulf,between May-July, dust can effect the airports at any time, and strong surface north-west winds (SHA-MAL) of 20-25 knots can seriously reduce visibility in rising sand and dust. Average visibility is 3000-4000 metres in dust, but can fall to about 1000 metres for a few hours after the onset of the SHAMAL, particularly in early June.
Easterly winds from the sea bring patchy fog or stratus at 500 to 1000 feet at Bahrain and Doha. Generally if Bahrain gets fog so will Doha; Dubai generally gets more fog than Bahrain, Northwest winds from sea can result in fog at Dubai.
Land breeze from the west-south-west and sea breeze from the east-north-east can be pro-nounced during summer and autumn.
NOTE: During summer, rapid cooling at the surface after sunset can produce a marked inversion above 400 feet, and pilots should be alert to the associated problems, as seen in the following example:
July:
– 2000 feet 40º SAT – 1000 feet 40º SAT
– 500 feet 40º SAT
– Below 500 feetdropping rapidly to 31º on the ground.
1.1.2.1. Jetstreams and Upper Winds
Jetstreams are absent over the routes. Light westerly winds becoming variable in the Gulf Area and N-East to S-East towards Karachi.
1.1.2.2. Turbulence and Windshear
Practically no turbulence due to lower wind velocities. However, the approach path to aero-dromes in the Middle East and Gulf desert areas are subject to sometimes very strong wind-shears and/or inversion.
1.1.2.3. Tropical Cyclones
Moving in from the Arabian Sea they may very occasionally affect the Karachi area.
1.1.2.4. Dust and Sand Stands
See (Winter/Spring), however more frequent in summer.
WEST ASIA AND MIDDLE EAST WEATHER 1.1.2.5. ITCZ Inter Tropical Convergence Zone (Monsoon)
They ITCZ may reach as far as Karachi in midsummer but not every year.
WEST ASIA AND MIDDLE EAST WEATHER
I N T E N T I O N A L L Y L E F T B L A N K
EUROPEAN WEATHER
1.2. EUROPEAN WEATHER
1.2.1. Cyclonic SystemsThe weather is determined primarily by its situation in relation to the Icelandic low, and Azores high and the alternating high and low pressure systems of Asia. The general drift of weather is from west to east and the absence of any pronounced north to south mountain barrier enables cyclonic systems from the Atlantic to penetrate far into the continent. This region is therefore one of transition between oceanic and continental conditions, the latter becomingly more dominant towards the east and south-east.
– To the north of the British Isles into the Barents Sea and thence into north Russia.
– East-north-east across the British Isles or France to northwest Russia.
– From Iceland southeastwards to the Baltic Sea and thence to western Russia.
The areas to the south of the tracks are affected principally by the fronts of the depressions and by alternate warm and cold air masses. A common situation occurs with a low over north-ern Russia and the cold front trailing across Poland to central France. On approaching the Alps, the cold front often slows down and gives rise to a wide belt of cloud and rain. Waves on the front may develop into small but vigorous lows which move rapidly east-north-east.
Sometimes the main low to the northeast becomes very deep and a broad current sweeps over Western Europe, carrying the cold front through to the Mediterranean.
Occasionally lows develop over the continent itself, more especially in summer and in a moist unstable air mass. These thermal lows give much rain and thunder with extensive masses of cloud, but outside the rain areas the clouds are usually isolated.
Another type of low develops chiefly in winter and spring between the Alps and the middle Danube in association with warm moist air spreading northwards from the central and east-ern Mediterranean.
The warm front is better defined in the upper levels than at the surface but it gives rise to extensive low cloud over Germany and Poland, possibly extending to the Low Countries and even to eastern England Precipitation is also widespread and may reach the ground as snow.
1.2.2. Anticyclonic Systems
The anticyclones affecting Europe are mainly of three types:
a) Extensions of the Azores high -these consist of tropical air and occur mostly in summer.
b) Extensions of the Siberian high, consisting of polar continental air and occurring chiefly in winter and early spring.
c) Those which approach from northwest following a cold front associated with a depression over northern Scandinavia or Russia. These consist of polar maritime or even Arctic air and occur in all seasons.
EUROPEAN WEATHER
Whereas anticyclones of type (c) are usually migratory, those of (a) and (b) often persist for several days or even weeks.
1.2.3. Winds
Great variability in both speed and direction is found at all levels although the prevailing direc-tion is westerly. Periods of easterly or northeasterly winds are usually associated with a west-ward extension of the Siberian high. The westerlies generally increase with height; at about 30,000 feet in the jet streams, the axis of which are often situated parallel to the surface fronts but displaced a few hundred miles towards the cold side, speeds of well over 100 knots are common. Winds in summer are generally lighter than in winter.
1.2.4. Cloud and Precipitation
With the prevalence of Cyclonic activity in winter (especially in the west and north) and of convection in summer, there is much cloud and rain throughout the year. The mean cloud amount varies only from about 6 oktas in winter to 5 oktas in summer and shows little varia-tion geographically, but the annual rainfall decreases steadily from about 1,000 millimetres in the extreme west to less than 500 millimetres in the east, except for the increased falls which are to be expected on high ground.
Away from the western coastal strips where most rain falls in winter, the wettest period is usu-ally late summer or -autumn and the driest period late winter or early spring. Precipitation is liable to fall as snow during the winter months, more especially in the east and southeast where the ground may remain snow-covered for long periods.
1.2.5. Visibility
The greatest difficulty for aviation in Europe is the high frequency of fog and very low cloud.
Both of these occur readily in air masses of maritime origin, little cooling being required to produce condensation. The fog may become widespread and dense in anticyclonic condi-tions and is aggravated by smoke in industrial areas. In summer, fog is infrequent except over the sea and coast where it drifts on-shore. Cloud on the surface of hills is liable to occur at any time of year.
1.2.6. Ice Accretion
The 0ºC isotherm in winter is often at or near the surface, especially in central and Eastern Europe. Combined with the large cloud amounts, this results in high frequency of conditions favourable for airframe icing. Even in summer the risk remains high. Severe conditions occur when an unstable maritime air mass passes over a coast or over hilly country with the forma-tion of extensive convective clouds. This may occur for example over northwest and central Germany with an air supply from the North Sea. Icing is also likely to be severe in a mass of warm front cloud which develops instability on approaching a mountain range.
EUROPEAN WEATHER
1.2.7. Fog
Fog is the critical weather feature at Frankfurt, London, Milan, Munich, Paris and Manchester.
The worst period for fog is from mid September to mid October, but this often extends to mid December.
EUROPEAN WEATHER
I N T E N T I O N A L L Y L E F T B L A N K
SOUTH ASIA AND THE FAR EAST WEATHER - 1
1.3. SOUTH ASIA AND THE FAR EAST WEATHER - 1
(India, Sri Lanka, Malaysia, Singapore and Indonesia)1.3.1. Winter and Spring (December to June)
Fine weather season. Generally cool and dry. Generally less than 2/8 of cloud. Some excep-tions are: -
1.3.1.1. Malaysia, Singapore and Indonesia
The southern part of Malaysia and Singapore are still affected by frequent towering cumulus and thunderstorms with heavy showers.
1.3.1.2. Sumatras
Heavy squalls mostly active late in the night to early morning will be found in the straits of Malacca in spring/summer and autumn. Singapore has an average of 404 thunderstorms per year.
1.3.1.3. Jetstreams and Upperwinds
December to March are the months of greatest jetstreams activity. Main axis north of Karachi -New Delhi, Kolkata- north of Yangon. Average strength 60 knots weakening towards Rangoon/Bangkok maximum around 100 knots. On the route from Colombo to Singapore the upper wind is normally from east to southeast between 10-20 knots.
1.3.1.4. Turbulence
Clear Air Turbulence associated with the jet stream, light to moderate.
1.3.1.5. Thunderstorms and Tropical Cyclones
Occasionally a depression from the Mediterranean area may move across India, south of the Himalayas giving thunderstorms and northwest surface winds up to 50 knots, in the region of Kolkata. They are called the "NORWESTERS” Tropical Cyclones have a secondary peak in May and may be found in the Bay of Bengal.
SOUTH ASIA AND THE FAR EAST WEATHER - 1
1.3.2. Summer and Autumn (July to November)
This is the monsoon season monsoon means seasonal. A monsoon is a main wind flow that persists for a long period and then undergoes a complete reversal with change of season.
Winds result from the effect of uneven seasonal heating between the large landmass of Asia and warm Equatorial Seas. Summer monsoons blow towards low pressure over the heated land. Winter monsoons from high pressure over the cooled land.
The Southwest monsoon advances over Southern Indian Peninsula & Sri Lanka between 25th and 31st May every year. The monsoon advances in the form of two branches known as the Arabian Sea Current and the Bay of Bengal Current. The advance of the Inter Tropical Convergence Zone or the Intertropical Front over the latitudes of India is known as the advance of the Southwest monsoon. Normally the advance of the Southwest monsoon is her-alded by thunderstorms when the equatorial maritime air replaces the continental air. The ITCZ advances as far as 27N parallel and the entire India is in the grip of Southwest mon-soon by the 15th of July when the axis of the Inter Tropical Convergence Zone is located from the Northern parts of Rajasthan across the Gangetic plains into the head bay of Bengal.
Along the axis of the trough thundery precipitation is the characteristic feature throughout the season. Whereas the latitudes of Bombay is characterised by steady showery precipitation.
The inter tropical front or the Intertropical Convergence Zone is the boundary along which the trade wind currents of both hemispheres converge. Its position varies with the season, being located approximately 10 degrees South in January-February and 5 degrees North in July-August. The monsoon and the mean position of the ITCZ reaches Colombo and Singapore at the beginning of May, Bombay and Bangkok about 3–4 weeks later. The Inter Tropical Con-vergence Zone retreats again during October (BOM/BKK) and early November (CMB/SIN).
The Inter Tropical Convergence Zone consists of squalls with cumulus and CB activity over an area of 100 NM or more in width. Top of CB’s 50-60000 feet. Best flying altitude can some-times be FL280-300 below the widespread anvil.
West Coast of India (Bombay), Trivandrum and Sri Lanka get heavy rainfall under the influ-ence of the Arabian Sea branch of the Southwest monsoon. In fact the period of May / June are the peak period of rainfall activity. Similarly in this period (July / August) Eastern prov-inces of India namely eastern parts of Bihar, West Bengal (Kolkota) and Bangladesh (Dhaka) come under the influence of the Bay of Bengal Current of the Southwest monsoon.
During July and August intense low pressure systems called monsoon depressions originate over the head bay of Bengal and travel in West to North-westerly direction ushering rainfall along their tracks. These depressions cause widespread rainfall over India. When a monsoon depression moves Northwest from the head bay and located near Central India, Bombay experiences very heavy rainfall associated with squally weather.
Even though the activity of the Southwest Monsoon season extends from June to September, the whole season is not one of continuous rainfall activity. Barring the monsoon depressions which cause heavy rainfall along the path in which they travel, the rainfall activity in general over the India Sub-Continent also depends very largely upon the position of the monsoon trough.
SOUTH ASIA AND THE FAR EAST WEATHER - 1
When this trough occupies a more northerly position it is known or called a Weak or Break Monsoon condition. The Weak or Break Monsoon occurs when the whole country is under the Westerly wind sweep. This can be seen when the Bay of Bengal branch of monsoon is not affecting the northern parts of India and when there is no easterly wind flow to the north of the axis of the monsoon trough.
During such situations, the rainfall pattern over the country undergoes a striking change. The regions of the Himalayas get very heavy rainfall. The northern parts of Assam get very heavy rain and the rivers in the northeast regions become flooded. The rainfall activity generally decreases over the rest of the country. Cloud coverage is lesser during such periods and as a consequence, the temperature rises. Pressures also rises phenomenally over the central parts of the country. However, there is an increase of rainfall more of thundery activity over the interior parts of the South Peninsula. In fact, Madras gets thundershowers during such spells.
1.3.2.1. Aerodromes in the Region 1.3.2.1.1. Mumbai (Bombay)
The monsoon precipitation occurs in the form of pulses or waves over Bombay. Series of cloud patches move inland from the sea causing heavy showers over a short period followed by short breaks. During cloud bursts the visibility reduces below 800 metres. Within a short while the visibility improves well over 3 to 4 kilometres. Occasionally it rains very heavy con-tinuously over three to four hours. Generally the intensity of rainfall is heavy during the night and early morning hours. During the active monsoon period very strong surface winds gust-ing to 30 knots exceeds crosswind condition limits. Approach to RWY 27 will be very bumpy and runway breaking action poor.
1.3.2.1.2. Kolkata, Dhaka
The months of October, November and December are called the North East monsoon sea-son and is confined to the East of India. In this seasea-son East Coast of India and Bangladesh are very vulnerable to cyclonic storms.
1.3.2.1.3. Colombo
Colombo receives rainfall during the Southwest monsoon and the east coast of Sri Lanka during the Northeast monsoon season but Colombo Airport receives more rainfall during the Southwest Monsoon Season.
1.3.2.1.4. Delhi
During July and August Delhi Airport experiences heavy thunderstorm activity and some-times dust storms.
SOUTH ASIA AND THE FAR EAST WEATHER - 1
1.3.2.1.5. Chennai
Generally Chennai is a fair weather airport throughout the year except during the months or October and November, with a cyclonic storm close to the coast. Convective thunderstorms are common during the months of March, April and May due to tropical heat. Because of the geographical features of the West Coast rainfall in the rest of the Southern Peninsula gradu-ally decreases from West Coast to East Coast. Chennai Airport is on the East Coast can therefore be used as a suitable alternate to Colombo, Hyderabad and Bombay during the peak monsoon months.
The Southwest monsoon withdraws from North India by the middle of September. When the Inter Tropical Convergence Zone passes through the latitudes of 15 to 10 North, cyclonic storms originate in the Bay of Bengal and move in a north-westerly direction during the months of October and November. These storms are severe in intensity and strike the East Coast of India. Chennai is very much vulnerable for these storms to strike. Sometime the eye of the storm could pass through Chennai City resulting in surface winds of 100 to 120 knots accompanied by very heavy rain bringing hazardous weather to Chennai Airport. It is advis-able to skip Chennai Airport when a storm is centred about 50-100nm off the coast of Chen-nai. The Northeast monsoon affecting the coast of India ceases by the end of December.
The Southwest monsoon withdraws from North India by the middle of September. When the Inter Tropical Convergence Zone passes through the latitudes of 15 to 10 North, cyclonic storms originate in the Bay of Bengal and move in a north-westerly direction during the months of October and November. These storms are severe in intensity and strike the East Coast of India. Chennai is very much vulnerable for these storms to strike. Sometime the eye of the storm could pass through Chennai City resulting in surface winds of 100 to 120 knots accompanied by very heavy rain bringing hazardous weather to Chennai Airport. It is advis-able to skip Chennai Airport when a storm is centred about 50-100nm off the coast of Chen-nai. The Northeast monsoon affecting the coast of India ceases by the end of December.